Statistical determination of the MDC of apramycin. The MDC was the antimicrobial drug concentration that allowed a statistically significant increase in the number of Salmonella cells invading the Caco-2 cells. The result of an experiment with apramycin is shown as representative of the data acquired for each antimicrobial drug tested in this study. Probabilities of statistical significance were determined by analysis of variance. *, P < 0.05.